Twitter is a cool website where you can type any old thing into a box and send it out into the ether for the entire internet to read. Some people use it to joke around, some people use it to be like, "HEY INJUSTICE IS HAPPENING, WHOA #GETINVOLVED," and some people use it to roleplay as characters from Sonic the Hedgehog. It's a lot of fun, especially if you like heated arguments with total strangers.

Large institutions like corporations and government agencies use Twitter too, usually pretty badly. "Hey, we're a pizza company, send us pictures of you eating our pizza and hashtag them #pizzapics" is an example of a typical lousy tweet from one of these accounts. Generally institutions try to drum up something vague called "social engagement"—basically they want to get people tweeting good stuff about them so other people see those tweets and, I guess, come to think good thoughts about the institution who started the engagement campaign. The New York Police Department was probably thinking they could do one of those social-engagement thingies when they launched the hashtag #MyNYPD with this tweet:

What the person running the Twitter account probably failed to realize is that most people's interactions with the cops fall into a few categories:

1. You are talking to them to get help after you or someone you knew was robbed, beaten, murdered, or sexually assaulted.

2. You are getting arrested.

3. You are getting beaten by the police.

In category 1, you are probably not going to be like, "Oh, let me take a selfie with you fine officers so I can remember this moment," and the other two categories are not things that the NYPD would like people on social media talking about. Additionally, the people who use Twitter a lot (and who aren't Sonic the Hedgehog roleplayers) are the type who love fucking with authority figures. In any case, #myNYPD quickly became a trending topic in the United States, largely because people were tweeting and retweeting horrific images of police brutality perpetrated by New York City cops. Here are some of the notable ones, starting with VICE's own Molly Crabapple tweeting a photo of her arrest at an Occupy Wall Street protest: